TCCA Chemical Hazards

The ongoing chemical incident at the Bio-Lab facility in Conyers, GA has caused significant damage to the Bio-Lab facility (not yet fully documented in the press), the evacuation of thousands of people in the area surrounding the facility, and the on-again-off-again shelter in place for even more thousands of residents outside of the evacuation zone. The source of these problems is the chemical trichloroisocyanuric Acid (TCCA), a bleaching agent commonly used for the disinfection of swimming pools and spas. Typically sold in small quantities most people do not consider this to be a dangerous chemical.

As I noted in this morning's post, Bio-Lab has had problems in the past with safety incidents related to TCCA. The CSB’s report (pg 13) on the May 2020 incidents describes the hazards associated with TCCA:

“Trichloroisocyanuric Acid (TCCA), a chlorinating agent, is often used as a sanitizer for swimming pools and hot tubs. It is a white solid substance manufactured at the Bio-Lab facility and available as a powder, compacted tablets, and granules (Figure 2). In large bodies of water, such as pools, TCCA breaks down slowly to release hypochlorous acid (HClO), as shown in Figure 3, which kills bacteria, algae, and other microorganisms as intended. When TCCA instead comes in contact with a small amount of water, it can experience a chemical reaction causing heat generation [1, pp. 2-3] and the decomposition of the TCCA. When TCCA reacts and decomposes, it produces toxic chlorine gas [2, p. 2622] and can produce explosive nitrogen trichloride [3, p. 1]. According to the U.S. Environmental Protection Agency (EPA), “Even a small amount of water splashed on the [pool] chemical may in some cases trigger a strong reaction” [1]. Water-reactive materials may violently react, produce toxic or other hazardous gases, or evolve enough heat to cause self-ignition or ignition of nearby combustibles upon water exposure [4, pp. 400-17]. TCCA is a Class 1 oxidizer, and TCCA “[r]eacts with combustible materials, ammonia salts, or foreign substances, resulting in fire [5, pp. 49-148]. Bio-Lab’s TCCA safety data sheet (SDS) states that a fire involving TCCA should be flooded with water.”

What this means when a storage facility for a TCCA manufacturer becomes involved in an incident, is that past a certain size, the situation becomes unmanageable. If the building collapses from the affects of the fire (as has appeared to have happened this weekend) an indeterminate number of individual containers are going to become compromised. Non-flooding amounts of water are going inevitably come in contact with the exposed TCCA, starting the decomposition process all over again. Heat from the reaction in the newly damaged container will provide sufficient heat to compromise additional plastic containers that had not already been damaged. Either additional water will reach these containers, or the exotherm from nearby containers will increase the temperature to begin the decomposition process in a new site. Shifting wreckage will damage further containers. And so on and so on until all of the containers are reduced to melted plastic slag. Hopefully, that will happen before anyone starts to tear down the remains of the damaged building.